The major objectives of this project are the elucidation of the biochemical mechanisms by which insulin, catecholamines, growth hormone, glucocorticoids along with other hormones and drugs act on rat liver cells and fat cells obtained from adipose tissue. Particular attention is placed on the role of cyclic AMP in the regulation of lipid mobilization from adipose tissue. The regulation of cyclic AMP accumulation in fat cells by adenosine and free fatty acids is being examined by measuring cyclic AMP accumulation in cells, cyclic AMP release to the medium, adenylate cyclase activity of fat cell ghosts and other membrane preparations, protein kinase activity of fat cell homogenates and cyclic AMP phosphodiesterase activity of various fractions from homogenized fat cells. We are currently comparing the hormonal regulation of lipolysis and the role of cyclic AMP in fat cells from chickens as compared to those from rats as the chicken fat cells do not appear sensitive to feedback regulation of cyclic AMP accumulation by the products of lipolysis. We are also examining the role of cyclic nucleotides in glycogenolysis by fish hepatocytes and of gluconeogenesis by rat hepatocytes.